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> Reference material for ROW_NUMBER function

# ROW_NUMBER OVER

Returns a unique row number for each row within the requested window.

For more information on usage, please refer to [Window Functions](/reference-sql/functions-reference/window).

## Syntax

```sql theme={"theme":{"light":"css-variables","dark":"css-variables"}}
ROW_NUMBER() OVER ([PARTITION BY <partition_by>] ORDER BY <order_by> [ASC|DESC] )
```

## Parameters

| Parameter        | Description                                                                                                       | Supported input types |
| :--------------- | :---------------------------------------------------------------------------------------------------------------- | :-------------------- |
| `<partition_by>` | The expression used for the `PARTITION BY` clause.                                                                | Any                   |
| `<order_by>`     | The expression used in the `ORDER BY` clause. This parameter determines what value will be used for `ROW_NUMBER`. | Any                   |

## Return Type

`INTEGER`

## Example

In this example, players in each game level are assigned a unique player ID using `ROW_NUMBER`.

<div className="query-window">
  ```
  SELECT
      nickname,
      level,
      ROW_NUMBER() OVER (PARTITION BY level ORDER BY nickname ASC) AS player_id
  FROM
      (VALUES
          ('kennethpark', 9),
          ('ymatthews', 9),
          ('sabrina21', 10),
          ('burchdenise', 11)
      ) AS t(nickname, level)
  ORDER BY level, nickname;
  ```

  | nickname <span>text</span> | level <span>int</span> | player\_id <span>long</span> |
  | :------------------------- | :--------------------- | :--------------------------- |
  | kennethpark                | 9                      | 1                            |
  | ymatthews                  | 9                      | 2                            |
  | sabrina21                  | 10                     | 1                            |
  | burchdenise                | 11                     | 1                            |

  <p><span>Rows: 4</span><span>Execution time: 5.33ms</span></p>
</div>